This invention relates to a method for producing 5-alkylidenenorbornene-2. More paticularly, the invention relates to a method for producing 5-alkylidenenorbornene-2 by isomerizing 5-alkenylnorbornene-2.
It is generally known that 5-alkylidenenorbornene-2 is used as the third component of the so-called EPDM rubber which is a copolymer of three materials, ethylene, propylene and nonconjugated diolefin. Further, it is also known that 5-alkylidenenorbornene-2 is produced by isomerization of 5-alkenylnorbornene-2. For the above isomerization, various kinds of methods have been proposed, for example, a method for isomerization using a catalyst of alkali metal-carrier type (U.S. Pat. No. 3,347,944); a method using a catalyst consisting of alkali metal strong base such as potassium hydroxide and an aprotic dipolar solvent such as dimethylsulfoxide (ibid.); a method using a catalyst of a mixture of a sodium-potassium alloy and hexamethylphosphortriamide (French Pat. No. 1,529,455); a method using a catalyst of a mixture of alkali metal amide such as sodium amide and a nitrogen-containing solvent such as ethylenediamine (French Pat. No. 1,534,366); and a method using an organic alkali metal catalyst (French Pat. No. 1,525,727) are known.
There are, however, several disadvantages in the above known methods that preparation of the catalyst is difficult, a large amount of catalyst is necessary as the catalytic activity is low, severe raction conditions such as a high reaction temperature are necessary, or a large quantity of expensive solvent which is difficult to separate from the product of 5 -alkylidenenorbornene-2, must be used.